This invention is concerned generally with flow control in a lateral re-entry system between a main bore and a lateral bore in a production system.
In the oil and gas industries many types of well or borehole exist. Many are vertical shafts which pierce the earth and rock to a depth of thousands of feet. Where the wellbore penetrates an oil or hydrocarbon bearing rock strata, the hydrocarbons may be produced to surface. It is common for many layers of hydrocarbons to be present at varying depths, often isolated from each other by layers of impermeable rock.
Recent developments in technology have allowed drillers to deviate wells from the vertical in order to reach a target which may be distant from the wellsite or may allow complete drainage of a pool or field of hydrocarbons by using many wells from one central point. More recently, it has been possible to drill xe2x80x9chorizonalxe2x80x9d wells by deviating out by up to 90 degrees from the bottom of a vertical shaft. This technique may increase productivity by allowing access to a greater section of the rock strata than would have otherwise been possible in the vertical plane. This is advantageous when only a limited vertical footage of hydrocarbon bearing rock is present.
More recently, it has been possible to drill what is termed a xe2x80x9clateralxe2x80x9d extension from a vertical well effectively allowing the construction of two wells with the saving of the cost of the vertical section of one. An.example of this is shown in FIG. 1 of the accompanying drawings. Following this theme, two or more laterals may be drilled with similar savings. The laterals may be highly deviated or horizontal in order to specifically target the hydrocarbons and provide optimal recovery of hydrocarbons from the well.
Following the drilling phase, multilateral wells are completed with pressure containing tubing in order to allow safe production of hydrocarbons to surface. At the junction of the laterals, packers provide a pressure isolation barrier between the lateral and the main bore. Devices may be installed at this point to regulate or shut off flow from the lateral. These devices are situated in the xe2x80x9ctrunkxe2x80x9d or main bore section and are presently only recoverable by removing all the pressure containing tubing, packers and associated equipment collectively called the xe2x80x9ccompletionxe2x80x9d. This is an obvious disadvantage if remedial work or investigation of any kind is required in the lateral as a drilling rig and crew will be required to remove the completion. This is a very costly operation and may be required during the lifetime of the well for a number of reasons. Also, for safety reasons, the well will have to be xe2x80x9ckilledxe2x80x9d by filling with mud and pumping mud around the wellbore before the completion can be removed. This process may damage the oil bearing formations and reduce future recovery.
Remedial work and/or investigation will be required if there is water production. Should one lateral begin producing large amounts of water, not only will the produced water have to be processed on surface, but the water will displace oil which might otherwise have been produced. The water will also reduce the overall efficiency of the well. In this situation it is normal to plug or close off the area which is producing the water. This may entail plugging off the end section of a lateral.
The invention has therefore been developed primarily, though not exclusively, with a view to provide a method which may obviate these disadvantages by providing a means to re-enter a producing lateral in order to measure and deal with water production without killing the well and without removing the completion but also to provide separate remote control of the lateral when in its normal producing mode.